Tom Lehrer, the man who wrote Poisoning Pigeons in the Park, has been described as "the most brilliant song satirist ever recorded". His songs are the stuff of your adolescent imagination: subversive send-ups of the boy scouts, religion, pollution, plagiarism, prudishness. They are twisted, erudite parodies of the perverse: a necrophiliac's love song, a Masochism Tango, a nuclear military march. They are acid attacks on political expedience: " 'Once the rockets are up, who cares where they come down? That's not my department,' says Wernher von Braun."

So when you meet him, Lehrer comes as rather a surprise. Smiling, elfin, a bit stooped but slim and spry at 72, he is nothing so much as sweet. Sure, he confesses to still composing such questionable ditties as Bye- bye, Baby (about "partial-birth" abortion), but now it's strictly to appal himself. He bemoans the decline of civility and grammar and the collapse of the liberal consensus that made his songs of the 50s and 60s seem daring and safely hilarious at the same time.

But he does not pine for the performing career that made him a sensation in nightclubs and concert halls (his last major paid appearance was 33 years ago). He does not mourn the muse that seemed to desert him after Vietnam made it harder to be funny about serious things. Or, as he once put it: "Political satire became obsolete when Henry Kissinger was awarded the Nobel peace prize."

Why should Lehrer be glum, after all? A Harvard-trained mathematician, he spends the cold half of the year in a beautiful college town at the edge of the Pacific, teaching maths at the University of California at Santa Cruz, where he has worked since 1972, after stints at Harvard, Massachusetts Institute of Technology and Wellesley College. He still spends the warm half in Cambridge, Massachusetts, where he first went to Harvard as a precocious 15-year-old.

And Rhino Records today issues The Remains of Tom Lehrer, a boxed set of his works, including a handful of previously unreleased recordings such as I Got It From Agnes (you guessed what "it" is) and Hanukah in Santa Monica, a hymn to Jewish holidays that rhymes Shavuos with East St Louis. (He decided against a line that rhymed a body part with Passover).

"Amazing," Lehrer says modestly of the enduring appeal of his songs, which first saw the light in informal performances in Cambridge, then on a 10in, self-released LP in 1953 and later in the best-selling 1965 album That Was the Year That Was.

Professor Lehrer may stick to the blackboard and not the microphone these days, but his gift for verbal distillation has not deserted him. "When I was in college, there were certain words you couldn't say in front of a girl," he writes in the sleeve notes for the new collection. "Now you can say them, but you can't say 'girl'. "

Lehrer is not a recluse, though he resists all publicity unless he has something to sell, refuses television interviews (because he'd be asked to perform and then might be recognised in airports) and admits having encouraged rumours that he was dead, in the vain hope of cutting down on his junk mail. No, Lehrer is a man who had his moment, enjoyed it, banked his royalties and moved on. "I don't feel the need for anonymous affection," Lehrer said. "If they buy my records, I love that. But I don't think I need people in the dark applauding."

Besides, he adds: "I'm not interested in promoting myself, or revealing to total strangers anything about me. That's not my job. I read some of these things with people who will tell you about their abortions, and their affairs and their divorces and their breakdowns and their parents, and why are they doing that? And I'm sure if you asked them how much money they made last year, they'd tell you it's none of your business."

Lehrer grew up in New York, where his father manufactured ties and his mother took him to musical theatre, igniting a passion that has never wavered. He went to camp with a songwriter named Stephen Sondheim, whom he calls "the greatest lyricist the English language ever produced", but he wasn't especially close to him at the time. "I'm two years older, and when you're 10, you don't hang out with eight-year-olds," according to Lehrer.

He was also good at maths, not uncommon for musicians. "There's something mathematically satisfying about music: notes fit together and harmony and all that. And mathematics has to do with abstractions and making connections."

Formalities like a PhD and tenure eluded him, but Lehrer had a gift for pastiche, borrowing and echoing musical styles and sources from Gilbert and Sullivan to Danny Kaye. Indeed, Lobachevksy, his paean to plagiarism featuring the name of a real, dead, nonplagiarist Russian mathematician, is itself one big inside joke: "A direct plagiarism," Lehrer said, of a Danny Kaye routine about Stanislavsky.

The Lehrer canon, only about 50 recorded songs, falls into three basic clumps: his first two albums from the 50s, with black-comic parodies of various song styles and genres; the overtly political satire of That Was the Year That Was (a collection of songs contributed to the US television programme of the same name and recorded live at the Hungry i. nightclub in San Francisco); and everything else, including Silent E, his tribute to the transformative powers of spelling ("Who can turn a can into a cane?").

The early, risqué songs were well ahead of their time. Be Prepared, his goof on the boy scouts, for example, ends: "If you're looking for adventure of a new and different kind,/And come across a girl scout who is similarly inclined,/Don't be nervous, don't be flustered, don't be scared./Be prepared!"